The body temperature of mammals is normally tightly controlled by an autonomic regulatory system referred to herein as the thermoregulatory system. A primary effector of this regulatory system is blood flow to specialized skin areas where heat from the body core may be dissipated to the environment. Normally, when body and/or environmental temperatures are high, the dilation of certain blood vessels favors high blood flow to these surfaces, and as environmental and/or body temperatures fall, vasoconstriction reduces blood flow to these surfaces and minimizes heat loss to the environment.
Strategic inducement of vasodilation in targeted portions of the body, such as the extremities, may exert positive therapeutic benefits in remote regions of the body. For example, manipulating heat transfer across the skin may change the core temperature of the mammalian body in response. Unfortunately, it may be difficult to induce such changes to an extent sufficient for therapy, given the human body's refined ability to thermoregulate to maintain temperature homeostasis or normothermia.
Applying heat and subatmospheric (negative) pressure to a hypothermic individual's skin, increases in body core temperature may be achieved (see, e.g., Grahn et al., “Recovery from mild hypothermia can be accelerated by mechanically distending blood vessels in the hand,” J. Appl Physiol. (1998) 85(5):1643-8). Other therapeutic applications for cooling the skin have also been described; e.g., in treating cancer as described in U.S. Pat. No. 7,182,776 to Grahn. However, therapeutic applications for continuously applying heat to the skin after the core body temperature reaches, or is at, normothermia to increase microvascular circulation to treat conditions whose symptoms may include pain and inflammation have not been demonstrated.
U.S. Pat. No. 7,160,316 to Hamilton describes apparatus and methods for regulating body core temperature using an appendage chamber having a heat exchange element and configured to maintain vacuum conditions. The appendage chamber includes a strap to secure a person's hand on the heat exchange element. In practice, such a strap does not accommodate hands of different sizes: the strap may be too loose on small hands and may cause vasoconstriction of the arteriovenous anastomosis vascular area in the palm of large hands because the palm is pressed too hard against the heat exchange element. Additionally, the appendage chamber includes a hand seal configured to seal an appendage within the appendage chamber. Such a hand seal may cause leakage and does not provide the proper characteristics for maintaining a vacuum in the appendage chamber.
U.S. Pat. No. 6,846,322 to Kane describes apparatus and methods for manipulating body core temperature using an appendage chamber configured to maintain vacuum conditions. The appendage chamber includes a first flexible member and a first energy element disposed in an upper portion of the appendage chamber and a second flexible member and a second energy element disposed in a lower portion of the appendage chamber. The first flexible member is configured to enhance the surface contact between the first energy element and an upper portion of an appendage placed within the appendage chamber while the second flexible member is configured to enhance the surface contact between the second energy element and a lower portion of the appendage. The system described in Kane suffers from a number of drawbacks, including the use of multiple elements for delivering thermal energy to the appendage, thereby increasing manufacturing cost and complexity, and providing multiple failure modes.
In view of the foregoing drawbacks of previously known systems, it would be desirable to provide a robust and economical system for effecting whole body heating to increase whole body circulation.